Simulation of complex infrared radiation patterns from missiles for the purpose of evaluating and designing infrared detectors for tracking such missiles requires a capability of creating high resolutions dynamic infrared images of a controlled or predetermined pattern and pattern history. There is presently no good means available by which this can be accomplished. The present invention is a novel configuration of a reflection mode liquid crystal light valve for use as a visible-to-infrared dynamic image converter whereby the more easily controlled and observed visible image pattern may be used to produce an infrared image pattern for such purposes. The device employs an infrared reflecting and visible transmitting indium-tin-oxide film which also serves as a conductive electrode for the device.
The general development of light valve technology is illustrated by such patents as U.S. Pat. No. 3,824,002 issued to Terry D. Beard on July 16, 1974 and U.S. Pat. No. 3,976,361 issued to Lewis M. Fraas et al on Aug. 24, 1976, both of which are assigned to the assignee of the present application. Previous efforts to use such light valves for conversion of visible-to-infrared images have attempted to operate in the transmissive mode whereas such light valves are in fact inherently reflective devices. It has heretofore been thought that to convert such transmissive light valves to reflection mode, which is advantageous for increased liquid crystal retardation, would require a dielectric mirror. For operation in the 8-14 micron infrared region, this would require thick quarter-wave films, and thus a large total mirror thickness. This could result in increased surface roughness and stress failure of the mirror. The indium-tin oxide dichroic mirror configuration used in the present invention permits a high infrared reflectivity and visible transmission in a film less than 0.3 microns thick.
It is an object of the present invention to provide a liquid crystal light valve suitable for converting a visible wavelength dynamic image to an infrared wavelength dynamic image.
It is a further object of this invention to provide such a light valve using a thin dichroic conductive electrode film which is transmissive to visible wavelength radiation and reflective for infrared radiation and which may also serve as an electrode for the device.